diff --git a/testing/cffi0/test_verify.py b/testing/cffi0/test_verify.py
index b7710932..a6ca23cd 100644
--- a/testing/cffi0/test_verify.py
+++ b/testing/cffi0/test_verify.py
@@ -2174,22 +2174,23 @@ def test_verify_dlopen_flags():
     ffi1 = FFI()
     ffi1.cdef("extern int foo_verify_dlopen_flags;")
 
+    modulename = "_cffi_test_verify_dlopen_flags_%d" % random.randint(0, 1000000000)
     lib1 = ffi1.verify("int foo_verify_dlopen_flags;",
                        flags=ffi1.RTLD_GLOBAL | ffi1.RTLD_LAZY,
-                       modulename="_cffi_test_verify_dlopen_flags")
-    lib2 = get_second_lib()
+                       modulename=modulename)
+    lib2 = get_second_lib(modulename)
 
     lib1.foo_verify_dlopen_flags = 42
     assert lib2.foo_verify_dlopen_flags == 42
     lib2.foo_verify_dlopen_flags += 1
     assert lib1.foo_verify_dlopen_flags == 43
 
-def get_second_lib():
+def get_second_lib(modulename):
     ffi2 = FFI()
     ffi2.cdef("extern int foo_verify_dlopen_flags;")
     lib2 = ffi2.verify("int foo_verify_dlopen_flags;",
                        flags=ffi2.RTLD_GLOBAL | ffi2.RTLD_LAZY,
-                       modulename="_cffi_test_verify_dlopen_flags")
+                       modulename=modulename)
     return lib2
 
 def test_consider_not_implemented_function_type():
@@ -2257,7 +2258,7 @@ def test_implicit_unicode_on_windows():
 
 def test_use_local_dir():
     ffi = FFI()
-    lib = ffi.verify("", modulename="test_use_local_dir")
+    lib = ffi.verify("", modulename="_cffi_test_use_local_dir")
     this_dir = os.path.dirname(__file__)
     pycache_files = os.listdir(os.path.join(this_dir, '__pycache__'))
     assert any('test_use_local_dir' in s for s in pycache_files)
diff --git a/testing/cffi0/test_vgen2.py b/testing/cffi0/test_vgen2.py
index 34147c87..2cd1634c 100644
--- a/testing/cffi0/test_vgen2.py
+++ b/testing/cffi0/test_vgen2.py
@@ -3,7 +3,8 @@
 
 # This test file runs normally after test_vgen.  We only clean up the .c
 # sources, to check that it also works when we have only the .so.  The
-# tests should run much faster than test_vgen.
+# tests used to run much faster than test_vgen, but since we randomize
+# the module names, it needs to recompile everything.
 
 def setup_module():
     cffi.verifier.cleanup_tmpdir(keep_so=True)